The objectives of this project are: (1) to establish the physiologic basis of the third heart sound (S3). (2) to determine the utility of a new transducer (Surface Velocity Analyzer or SVA) to record velocity of chest wall movements over the precordium as a more sensitive indicator of the disturbed physiology responsible for the S3. (3) to apply the transducer in a clinical setting such as the Coronary Care Unit in order to monitor the course of critically ill cardiac patients and the effects of pharmacologic and hemodynamic interventions. Preliminary studies using measurements from angiocardiograms have shown that in diastolic overload conditions such as mitral and aortic regurgitation in contrast to normals the ventricle reaches its maximal velocity of filling in the long axis after it does in the short axis. The S3 in such patients coincides with long axis filling. Subsequent studies will attempt to achieve the following steps: (1) determine the pattern of ventricular filling velocity in patients with and without S3 by means of range-gated Doppler studies in conjunction with 2-D echo for accurate localization of the intracardiac Doppler observations. (2) establish the relationship between the filling patterns that are conducive to S3 generation and velocity of precordial chest wall movements as perceived via the SVA. (3) study patterns of ventricular filling in dyskinetic ventricles by means of frame-by-frame analysis of angiocardiograms. A topographical map illustrating contrasts in velocity of filling in various parts of the ventricle will be constructed with computer assistance in order to establish temporal relationships between S3 production and velocity of ventricular wall movements in areas of myocardium that retain their expansile capability in early diastole. (4) apply the SVA in clinical situations such as the Coronary Care Unit in order to detect alterations in velocity of precordial movement which constitute S3 equivalents so that therapeutic interventions may be introduced at a propitious time and their effect monitored to the end that the patient's vulnerability to sudden death might be altered in a favorable manner.